1. Field of the Invention
This invention relates to apparatus for moving bulk materials short distances and more particularly to a tethered vehicle which skids on the bulk material and in so doing, moves the material toward the tethered end of the vehicle. By bulk material is meant all types of flowable solid materials such as for example, crushed ores, rocks, coal, salt, sand and other granular materials and products such as grain and other particulate materials.
2. Prior Art
In recovering bulk materials from bins, hoppers, silos, the holds of barges and ships and other cargo and storage chambers, it is often difficult to maneuver the unloading device into the corners and close to the walls to recover all of the material. This is particularly true in the case of ships where the hatch usually does not expose the entire hold and the clam shell unloader or bucket ladder, or other continuous unloader which lifts the material out of the hold cannot reach under the deck.
Presently, it is common practice in unloading bulk material from ships, after the unloader has removed all the material it can reach, to lower a bulldozer into the hold to bring the material under the deck within range of the unloader. This method of recovering hard to reach material is tedious and inefficient, and, in the event of large amounts of residual material, constitutes a danger to the bulldozer operator from cave-ins.
It has been proposed that scraper conveyors can be lowered into the hold of a ship for moving bulk material toward a vertical transporter such as disclosed in U.S. Pat. No. 4,170,433. However, the apparatus requires two transversely mounted scraper conveyors and an operator to manipulate a digger arm movable along one of the scraper conveyors. Thus, this arrangement is cumbersome, difficult to set up and move from hold to hold and still requires an operator in the hold.
It has also been proposed to use a tethered vehicle to move bulk material. For instance, U.S. Pat. No. 3,153,476 suggests a self-propelled device in which a bladed cylinder is tethered by a winch and rotated by an internally mounted motor to move stone and ore. The device is moved laterally by differential operation of winches at either end of the cylinder or by making the cylinder in two halves and rotating the two halves at different speeds. U.S. Pat. No. 3,029,926 discloses another cylindrical device which is tethered by a winch. It recovers corn from the edges of a silo and is moved laterally by an operator who applies manual force to handles on the sides of the device. Both of these prior art tethered vehicles are difficult to maneuver and the latter device is obviously not suitable for large scale operations.